Testing samples of all food, beverages, and water for pathogenic microorganisms may not be practical because of the expense and because pathogenic microorganisms are rarely found in, for example, properly-processed food. Therefore, tests for the presence of indicator microorganisms are routinely used to test food and water to determine the likelihood of contamination with human pathogens. The presence of one or more indicator microorganisms can be an indication of fecal contamination, for example, and may indicate the potential presence of a pathogenic microorganism.
Coliform bacteria (“coliforms”) represent one example of indicator microorganisms. The coliform group includes a number of genera (e.g., Citrobacter, Enterobacter, Escherichia, Hafnia, Klebsiella, and Serratia) of rod-shaped Gram-negative bacteria that are found in large numbers in the feces of warm-blooded animals and are characterized by their ability to ferment lactose to acid and gas by-products. Although most coliforms are only associated with opportunistic infections in humans, some coliform bacteria (e.g., E. coli O157:H7 or other Shiga Toxin producing E. coli—STEC) are associated with a higher incidence of morbidity and mortality.
Members of the Enterobacteriaceae family of microorganisms represent another example of indicator microorganisms. In addition to the coliform bacteria, this family also includes a large number of other rod-shaped Gram-negative bacteria. Like coliform bacteria, the presence of Enterobacteriaceae microorganisms in a food or water sample can indicate the presence of fecal contamination and, thus, the possible presence of human pathogens (e.g., Salmonella enterica Enteritidis, Salmonella enterica Typhimurium, Shigella species, and Cronobacter species).
There is a need for efficient methods to test for the presence of pathogenic microorganisms in a sample.